This project is a part of our goal to study mutation in mammals in vivo utilizing monospecific antibodies against hemoglobin variants. Antisera against two mouse Hb's have been raised in horses and rabbits. A system has been developed that allows detection of the monospecific antibodies. Conditions are being optimized for labeling of red blood cells with the FITC-labeled antibodies. A sandwich technique for the labeling was developed for these cells. Monospecific antibodies are being purified for use in the system.